U.S. Geological Survey, 3215 Marine Street, Boulder, Colorado 80303, United States.
Environ Sci Technol. 2011 Apr 1;45(7):2575-83. doi: 10.1021/es104138y. Epub 2011 Mar 7.
Understanding the potential effects of increased reliance on wastewater treatment plant (WWTP) effluents to meet municipal, agricultural, and environmental flow requires an understanding of the complex chemical loading characteristics of the WWTPs and the assimilative capacity of receiving waters. Stream ecosystem effects are linked to proportions of WWTP effluent under low-flow conditions as well as the nature of the effluent chemical mixtures. This study quantifies the loading of 58 inorganic constituents (nutrients to rare earth elements) from WWTP discharges relative to upstream landscape-based sources. Stream assimilation capacity was evaluated by Lagrangian sampling, using flow velocities determined from tracer experiments to track the same parcel of water as it moved downstream. Boulder Creek, Colorado and Fourmile Creek, Iowa, representing two different geologic and hydrologic landscapes, were sampled under low-flow conditions in the summer and spring. One-half of the constituents had greater loads from the WWTP effluents than the upstream drainages, and once introduced into the streams, dilution was the predominant assimilation mechanism. Only ammonium and bismuth had significant decreases in mass load downstream from the WWTPs during all samplings. The link between hydrology and water chemistry inherent in Lagrangian sampling allows quantitative assessment of chemical fate across different landscapes.
了解增加对污水处理厂（WWTP）出水的依赖以满足市政、农业和环境流量的潜在影响，需要了解 WWTP 的复杂化学负荷特征和受纳水体的同化能力。溪流生态系统效应与低流量条件下 WWTP 出水的比例以及出水化学混合物的性质有关。本研究量化了相对于上游基于景观的源，从 WWTP 排放中排出的 58 种无机成分（从营养物到稀土元素）的负荷。通过拉格朗日采样评估了溪流的同化能力，使用示踪剂实验确定的流速来跟踪随水流向下游移动的同一部分水。科罗拉多州的博尔德溪和爱荷华州的四英里溪代表了两种不同的地质和水文景观，在夏季和春季的低流量条件下进行了采样。有一半的成分从 WWTP 废水中的负荷大于上游排水，一旦进入溪流，稀释是主要的同化机制。只有铵和铋在所有采样中从 WWTP 下游的质量负荷都有显著下降。拉格朗日采样中固有的水文和水化学之间的联系允许对不同景观下的化学命运进行定量评估。
